Fabricating rear crossmember?

[Gringo]

We've had two Defenders for five years, and the rust issues here in the British West Indies are terrible. I am giving up on our 110, but we want to keep the 90. I will have to take it completely apart to replace all the steel bits.

First order of business in the meantime is the rear cross member. It doesn't make sense to me to replace that with another one of that same thin steel. I am thinking of building a replacement from 1/4" steel box section, and not welding it to the frame but bolting it.

I had done that for the front bumper some years back and that worked out well.. Have any of you manufactured a solidly built bumper to replace the rear cross member? I'm looking for design ideas and the voice of experience.

Even a wooden bumper would be preferable to more thin steel. This island eats steel.

[CwazyWabbit]

There is a guy over here that makes 6mm thick cross members, I'll have a search and see if I can find some pictures.

I'm sure someone on this forum fitted one.

[CwazyWabbit]

Have a look at this post, a nicely made 6mm crossmember http://forums.lr4x4.com/index.php?showtopic=78577&p=672134

Using an open design makes it easier to clean out and also paint

[steve200TDi]

Hi,

What you could do it to box in a standard replacement which will help with the rust prevention and it filling up with mud, but making your own is an excellent idea!

If you haven't already, have a look at my build thread http://forums.lr4x4.com/index.php?showtopic=76471&page=1"]here[/url where I've designed a rear winch bumper for my TD5 and for my 200TDi, maybe you can get some inspiration.

If you say that you are dismantling it, then it will be a lot easier to fabricate and fit a new rear crossmember.

Have you got a list of requirements that you want the new crossmember to achieve?

Steve

[Retroanaconda]

Galvanise everything!

[LandyManLuke]

I built one from 160x80x5 box section. Its pretty similar to the standard cross member dimensions. I profiled the ends the same as a standard cross member, it's completely boxed in and sealed, with a pint of oil inside for good measure.

[Gringo]

Thanks for the info.

I don't want a new standard crossmember. It would double the cost to ship it here from UK, and it would be rusted out in three years, just like the previous two. Galvanizing is not an option. That capability does not exist here.

I am thinking of 1/4" steel plate, with two brackets welded to that to fit over the flush cut ends of the frame. Two bolts in each side to hold it.

Then using 2x8 or 2x10 lumber bolted to the flat plate as an alternative to more steel. I need just enough to support a 2x2 receiver hitch for towing our smaller boats. a rough sketch:

I never quite understood what all those holes and nooks and crannies were in the standard cross member were for, anyway, but I do know what I need is a simple bumper that can handle a beach environment 24 hours a day and doesn't require dismantling the vehicle to remove and service.

[Retroanaconda]

No galvanising in the whole country? That sucks

Not sure wood is a good idea, it will just hold water against the steel and rot it out faster surely.

[Frax]

I was also not happy with the width of steel on the rear x member, especialy when the rot sets in so when I rebuilt my 90 I made the x member with 4mm steel channel, I did enclose the back but left the ends open and drilled 1" drain holes in the bottom.

It was welded on but could have been bolted.

I did however galvie the thing - you will get an a look at it here http://forums.lr4x4.com/index.php?showtopic=64578&hl=frax

[Gringo]

Nice Job on that, Frax. Your front bumper is actually more of interest to me than the boxed in rear, although both approach works of art. I can't have anything with an inaccessible interior volume. The salt sticks to it, and away we go. Literally. I need something that I can keep exposed to air, inspect regularly, and can get to for rust removal and re-painting easily. A removable bumper. And by removable, I don't mean with a gas ax.

As for the wood, It would be spaced off the steel by enough to make sure it doesn't trap moisture. It's a shame nobody ever built fiberglass bodies for these. Even the aluminum is rotting away. Simply can NOT put two dissimilar metals in contact here, exposed to the environment. Even two grades of aluminum in contact is a problem. The rivets are stronger than the body, and connect it to steel. So the body loses.

I put a front bumper on a few years back with a hitch so I could push my boat uphill. That's sealed box section. Some photos of that are toward the end of this blog post at: http://2gringos.blogspot.com/2009/08/momentary-panics.html

Please ignore all the tropical blather and just scroll down til you see the front of the 90 photo.

[Frax]

The front bumber is one of these http://www.ws4x4.co.uk/product/90110-tubular-winch-bumper I must say that I was not impressed with the powder coating though, some of it was peeling by the time it arrived so it was stripped and recoated before it was fitted.

It is heavy and has done well though.

Like the pictures on the blog

[muddy]

I have just made one from the same box as Luke however in your situation I would use a bit of 10mm channel and if you feel that will rot out you could bolt it to the chassis with 4x M20s assuming suitable plates on the chassis 10mm-12mm angle?

Will.

[Hybrid_From_Hell]

http://forums.lr4x4.com/index.php?showtopic=40835&st=0entry3852872

[Gringo]

I really don't think anything with a horizontal plate or surface that will let mud get into it is worth the time and effort. These islands are marine limestone, formed at the bottom of the ocean. The very dirt of the roads here is the same salt content as seawater. The dust is corrosive. We have stopped putting radios in the Defenders. Automotive radios last about a year. I put a Sony marine radio in the 110, it lasted two years. Normal brake lines ( you call them pipes?) last 8-12 months. If we have to drive through puddles on the way to the airport, and leave one parked for a week or two, when we return I have to dismantle the hand brake drum and clean it out. I have to change the rearmost universal joint yearly. the local dealer offered us a total of $ 4500 for BOTH '06 Tdi's. They have less than 25,000 miles on them. each.

a rear bumper of channel with internal mounting plates is just more of the same. I don't want to copy the Land Rover design.....the only thing that would make them last longer is if I used thicker steel. they would still be ugly rusty things, just would take longer to die.

That's why I'm thinking the steel part needs to be a flat, vertical surface. No place for anything to puddle. Straps for the tow hitch receiver run to the frame, and those would be vertically oriented straps. I do like the idea of a sealed pipe with oil in it.

[Aragorn]

The crossmember isnt a "bumper", its a major structural part of the chassis...

You really cant go hacking it off and replacing it with a piece of wood!

[Snagger]

How about using stainless steel? It's more difficult to weld and cut/drill, but is should last longer.

As for the wood, don't do it - even with spacer washers, it's a humidity trap. The same an be said for the after-market aluminium chequer-plate cross member covers, which just promote the corrosion of the cross member that the plate has been applied to hide.

I think all you can do in your environment is repair (or ideally replace with a new galvanised version) your chassis and coat it with red oxide and marine paints on the outside and annually steam clean and spray the inside of it with old engine oil, which should give some protection but not trap the salt in place once it gets in there like wax would.

[Gringo]

The crossmember isnt a "bumper", its a major structural part of the chassis...

You really cant go hacking it off and replacing it with a piece of wood!

well, I respectively disagree. If Land Rover had built the entire frame out of laminated wood, they would still be functional.

[UdderlyOffroad]

I don’t understand why you want to use wood – presumably locally-sourced timber as it isn’t affected by your corrosive environment compared to steel? Still a moisture/dirt trap any however you attach it –even with spacers.

The reason Land Rover – as well as others use semi-enclosed box section is that it’s far stronger than open section. That said, if you look at a modern truck, you’ll see the ladder frame chassis is in fact C-section. I can only suggest you look at a bumper like Black Sheep’s design, and replicate that, with as many openings as possible to allow you to drain / clean out the dirt+salt. I just don’t think you’ll get away with having no horizontal section. If nothing else the rear tub needs something to sit on.

As for fabricating a completely enclosed section, I think that is ultimately fruitless. It may not initially allow foreign debris in, but when it does (not if), it then can’t get out again. Fine for a comp truck in the UK but I would think twice about doing it on a road-going vehicle.

I don’t know what your local vehicle roadworthiness test is (If any) – here in the UK a replacement cross-member will pass, provided it looks vaguely original and as strong as what it replaces (Hence Steve200Tdi not having any issues with his custom fabrication), but of course somewhere like Switzerland or Germany it would be a big fat no to anything except an original replacement.

To summarise: Fabricate something simple but semi-enclosed so you can regularly clean it out, and use the time saved to make some kind drive-on ramp (out of locally sourced timber?) to enable you to regularly inspect clean the underneath of the vehicle. Here in the UK we would use a pressure washer to blast away the salt/road debris, but I suspect that isn’t an option as fresh water is at a premium where you live?

[CwazyWabbit]

The use and attachment of wood shouldn't be dismissed, a good laminated hardwoord appropriately attached could last a long time and be incredibly strong, also damage to the timber will not cause it to instantly rot in a high salt environment unlike steel. When it comes to the question of corrosion to the steel where the wood is in contact with it I would suggest looking towards the boating industry to see how they deal with the issue. Something that the OP is no doubt well placed to check having looked at the pictures on his blog.

It's very easy to forget that we have a lot of industralised processes (like galvanizing) and a wide range of materials available that are either not available or prohibitively expensive to import to smaller islands.

[studmuffin]

How about using stainless steel? It's more difficult to weld and cut/drill, but is should last longer.

As for the wood, don't do it - even with spacer washers, it's a humidity trap. The same an be said for the after-market aluminium chequer-plate cross member covers, which just promote the corrosion of the cross member that the plate has been applied to hide.

I think all you can do in your environment is repair (or ideally replace with a new galvanised version) your chassis and coat it with red oxide and marine paints on the outside and annually steam clean and spray the inside of it with old engine oil, which should give some protection but not trap the salt in place once it gets in there like wax would.

Not sure if rectangular hollow section in true stainless is readily available but that would be my first choice.

If not I have heard that "Rock Hard" paint is the stuff they use on aircraft, and they dont paint them too often. Dont know the price or availability.

Wish you luck getting sorted.

Cheers

Barry

[Snagger]

Not sure if rectangular hollow section in true stainless is readily available but that would be my first choice.

If not I have heard that "Rock Hard" paint is the stuff they use on aircraft, and they dont paint them too often. Dont know the price or availability.

Wish you luck getting sorted.

Cheers

Barry

Aircraft paint isn't that good - it peels and scratches easily. Of course, it's on aluminium, not steel, but it really isn't anything special and you'd be surprised at how bad it is up close. Marine paint over red oxide is the best covering you'll manage, with grit blasting first to remove any surface rust and mill scale.

[Aragorn]

Bear in mind modern "red oxide" doesnt really provide any anti corrosion properties... Its just the same stuff as grey primer, but its been coloured red.

You'd be better using something like galvafroid or other similar cold galv paints as an undercoat.

[Bowie69]

That and 'Zinc rich primer' is really good, the tin weighs about twice a 'red oxide' tin of the same size, so easy to tell if it is any good.

[daveturnbull]

I have a crossmember that's basically just a piece of channel iron. It's nicely open to allow a good jet washing and about 10mm thick. The ends have been profiled so it looks like a standard one.

[heath robinson]

International do a 2-pack that's about as zinc and iron-oxide rich as is physically possible. If you leave it in a mixing cup you'll see about an inch (yes!) of metallic particles settle out at the bottom. The 15 litre main tub must weigh 35-40kg!

It's for painting industrial gear in salt water enviroments, like oil rigs...

I've used this stuff to undercoat my chassis, so I'll look at the number on the tub when I'm next in the lockup. It's a fetching sandy colour, and sticks like the proverbial to a blanket...

It's pricey (About 6 times more than what I paid for it, thankfully!), but worth a look if you're serious about stopping corrosion.